1. Field of the Invention
The present invention relates to a mounting unit to be used for mounting a cover member to a housing of an electronic apparatus, and more particularly, to a static-electricity-blocking mounting unit configured to prevent static electricity from flowing through a circuit board or the like of an electronic apparatus via a metallic screw configured to fix a cover member to a housing of the electronic apparatus.
2. Description of the Related Art
In an electronic apparatus provided with a circuit board having electronic components mounted thereto, when static electricity flows through the circuit board, the circuit board may malfunction or may be damaged. Therefore, it is one of significant challenges to prevent the static electricity from flowing through the circuit board, and various measures have been proposed conventionally against the static electricity.
It is another one of the significant challenges in the electronic apparatus to take measures against, for example, static electricity flowing via a metallic screw to be used for fixing an exterior component, such as a cover member, to a rear surface of the electronic apparatus. In particular, from the perspective of product layout, a large number of electrical components may be arranged on the rear surface of the electronic apparatus, and therefore, when the cover member configured to cover the rear surface, on which the large number of electrical components are arranged, is fixed to a housing of the electronic apparatus, a fastening position of the metallic screw needs to be taken into consideration. This is because the static electricity may flow through the circuit board via the metallic screw when the cover member is fixed in the vicinity of the circuit board with the metallic screw.
To address this, for example, the metallic screw may be coated with an insulating material having a high hardness, which can avoid the situation in which the static electricity flows through the circuit board via the screw. However, when the screw is made of such a material, manufacturing cost for the screw increases, and hence such a measure is not appropriate.
Further, for example, the fastening position of the metallic screw may be provided at a position distant from the circuit board so that the static electricity does not flow through the circuit board but flows to a ground, which can avoid the malfunction of the circuit board due to the static electricity. However, as in the above-mentioned case where a large number of electrical components are arranged on the rear surface of the housing from the perspective of product layout, the cover member may need to be fixed also in the vicinity of the circuit board with the metallic screw. To address this, there is disclosed a mounting structure for a cover member, in which a screw fastening seat for enclosing the metallic screw is formed on the housing to insulate the metallic screw (Japanese Patent Application Laid-Open No. H07-43809).
However, in the mounting structure for a cover member described in Japanese Patent Application Laid-Open No. H07-43809, the screw fastening seat is made of a resin material, and hence, when the metallic screw is fastened and unfastened repeatedly, fastening strength may decrease. To address this, for example, the seat may be made of an insulating material having a high hardness, but as described above, the manufacturing cost increases, and hence such a measure is not appropriate. Further, when the screw fastening seat is formed, there arises a problem in that change of the screw fastening position or other such flexible adaptation cannot be performed in a case of, for example, layout change of the electrical components.
Further, for example, an element for electrostatic measures may be added to the circuit board so that the circuit board does not cause malfunction even when the static electricity flows, which can avoid the malfunction of the circuit board. In this case, however, an electrostatic discharge immunity test needs to be conducted repeatedly every time the circuit is modified, with the result that efficiency decreases and cost increases.